Various metro and core optical networks utilize equipment supplied by many vendors that comprise varying degrees of technical advances. Often, technological evolution in optical networks has yielded smaller, more circuit-dense network equipment that requires less space and consumes less operating power. Telecommunications providers, and others employing optical networks, have an interest in reducing operational expenses and reclaiming office floor space by migrating to such newer systems. However, there are various circuit provisioning, equipment deployment and interoperability problems when introducing new equipment into legacy systems.
For example, various legacy versions of LUCENT TECHNOLOGIES' FT2000 Add Drop Ring (ADR) optical network utilize two different cross-connect fabric granularities on its high-speed interface OC48 (Optical Carrier 48) cards. Older versions of the FT2000 ADR (having one system per bay) use an STS-3 (Synchronous Transport Signal-3) granularity cross-connect fabric, while a more compact second generation FT2000 ADR system (having two systems per bay) uses the cross-connect rate of STS-1 granularity.
A problem lies with the older generation STS-3 granularity OC48 cards. The older version OC48 cards group circuits in packages of three STS-1s, and assign each STS-3 package to a low speed “drop” card. Low speed drop cards are configured as three DS3 (Digital Signal 3) connections per card, one OC3 per card, or one OC12 per card. In essence, an incoming OC48 signal is divided into sixteen STS-3 packages and terminated as STS-3 packages on the low speed drop cards. For example, a DS3 card will terminate an STS-3 package, an OC3 card terminates an STS-3 package, and an OC12 card terminates four STS-3 packages. Each timeslot within the STS-3 package corresponds to a specific drop port on the low speed drop card. Thus, ports on low speed drop cards become “locked” to a specific STS-3 package and are therefore “committed” to the far-end FT2000 equipment from which a specific STS-3 package originated. FIG. 1 illustrates the condition where three DS3 drop ports (ports 1-3) of a first FT2000 STS-1 granularity system (FT20000(1)) and a far end FT2000 STS-3 granularity system (FT2000(3)) are locked-up or dedicated to STS-3 packages transmitted therebetween. In this configuration, an intermediate FT2000 system (FT2000(2)) is also locked out of using the timeslot (for example, slot 16) dedicated to the STS-3 package transmitted from FT2000(1) to FT2000(3).
In addition, the most efficient use of the STS-3 granularity system is to assign contiguous drop ports whenever feasible. However, as circuits are added and subsequently dropped over time, the contiguous nature of the port assignments becomes lost. Thus, circuits are segmented across multiple STS-3 packages. To realign these manually is very expensive in terms of man hours, and any corrective actions will interrupt network operations while in progress.
Accordingly, there is a need for a method and apparatus for accommodating different switch matrix granularities in optical networks that addresses certain problems of existing technologies.